lowenstein



F. LOWENSTEIN.

RADIOSIGNA'LING APPARATUS.

APPLICATION FILED MN I9, I9I3.

Patented May 11, 1920.

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4' anotan) F. LOWENSTEIN.

RADIOSIGNALING APPARATUS.

APPLICATION FILED iAN. 19. 191B.

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Patented May 11, 1920.

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Patented May 11, 1920.

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F. LOWENSTEIN.

RADIOSIGNAUNG APPARATUS.

APPLrCMmN msn lAN. 19, |918.

.F.TLowenstein,

F. LOWENSTEIN.

RADIOSIGNALING APPARATUS.

APPLICATION FILED IAN. X9, 19H3 Patented May 11,-1920.

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RADloslGNALING APPARATUS.

V APPLICATnoN HLED iAN.19, |918. 1,339,772. Patented May 11, 1920.

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F. LUWENSTEIN.

RADIOSIGNALING APPARATUS.

APPLICATION FILED JAN. 19| I9IB.

Patented May 11, 1920.

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RADIOSIGNALING APPARATUS.

APPLICATION FILED 1Au.19,191a.

1,339,772. Patented May 11, 1920.

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F. LOWENSTEIN.

HADIOSIGNALING APPARATUS.

APPLICATION FILED 1AN.I9, 1918. 1,339,772. Patented May 11, 1920.

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F. LOWENSTEIN.

HADIOSIGNALING APPARATUS.

APPLICA'HON FILED MN. 19, 191B.

Patented May 11, 1920.

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RADIOSIGNALIN G APPARATUS.

Specification o! Letters latent.

Patented May ll, 1920.

Application lled January 19, 1918. Serial No. 212,816.

To all wlwm t may concern Be it known that I, Fnrrz LownNs'rmN, a citizen of the United States, residing at Brookl n, county of Kings, and State of New ork, have invented certain new and useful Improvements in Radiosignaling Aparatus; and l do hereby declare the follbwing to be a full, clear, and exact descriptlon of the invention, such as will enable others skilled in tlie art to which it appertains to make and use the same.

This `invention relates to radio signaling apparatus of a type in which provision is made Vfor rapidly changing the operating Wave length, either in sending or receiving, by means of mechanism operable to actuate simultaneously a reatance-varying device in each of two coperating oscillation circuits, such reactance-varymg devices comprising variable inductance or variable capacity, or both. p aratus of this neral character is describe and broadly c imed in my prior applications Ser. No. 569 24, lild June 28, 1910, and Ser. No. 10,592, ed February 25, 1915. The resent disclosure relates to certain improve embodiments of the broad principles disclosed in said prior applications, an also includes other novel features of neral application in this art.

For certain kinds of service, and especially in militar operations, it is necessar to employ porta le radio or wireless ing apparatus which must be characterized by reasonably high power and eiciency, lightness, compactness, resistance to shocks and rough usage generally, and also by simplicityand convenience of operation. Some of these requirements are to a certain extent mutually conicti with the result that it is difficult-to satis actorily meet'them Vali in one combined construction. For exai'nple, compactness, rigidity and massiveness of supporting structure, which are reuired for the portability, strength and c urabilit -essential to apparatus capable of withstan -ng rough treatment, are diicult to attain lwhlle complying with the requirement to guard against jumping of the current between high tension parts of high power apparatus. It is a primary object of the invention to provide apparatus which shall successfully meet all the .requirements in question and which shall at the same time embody features of improvement desirable in and of themselves, whether employed or not in portable apparatus of the specific character to be more particularly hereinafter described.

By way of concrete illustration and in order that the invention may be fully understood by those illed in this art, an especially desirable form of transmitter apparatus embod g the principles of the invention and s wn in the accom an ing drawings will be described in detail). llt 1s to be understood, however, that the invention is not limited to a transmitter nor to the specific construction here chosen for pur oses of explanation. In the drawings,

igure 1 is a front elevation of the assemb ed apparatus Fig. 2 is a plan view of the same;

Fi 3 isan elevation, partly in section on the 'line 3 3 of 2;

Fiis. 4 and 5 are longitudinal sections on the A1nes 4 4 and 5 5, respectively of )ig fis a front elevation of a part of the me change mechanism, on an enlarged e. Fi. 7 is a Section on the um 7 7 of Fig. 6;

ig. 8. is an enlar detail of the variometer coil and switc inelevation;

. 9 isa Isection on the line 9 9 of ig."'10 is a plan view oill an enlarged scale 0f -apart of .the apparatus Vshown i'n .2;

. 11 is a view of the same in side Iation, artly in section on the line ill-11 of f 12 is a sectional detail, on an ,emlargid scale, of a part of the selector mechamsm shownin 'F' 5;

13 and 1 am sections on the lines 13-513 and 14n-14 of Fig. 12;

`F i .g. 15 is a fgalgmetary view' in elevation of part ffthe ector mechanism shown in Fi :13and 14;

igs. 16 and 17 are a side elevation and plan', res ctivdly, of variable switch means em loy on th'e'loading coils;

18 is a section on the line 18-18 of Vwig. 19 is au enlarged detail, in elevation, o stopmeans for the transformer coupling method of mount' the liat conductor of which the coils are ormed;

Figs. 21, 22 and 23 are enlarged detail views of a terminal clip useful in tapping the transformer coils; and

F 24 is a circuit dia am.

The transmitter here i ustrated as a typical embodiment of apparatus within the scope of my invention, may be generally described as comprising an oscillation transformer having inductively related primar and secondary windings or coils, and loa ing coils in circuit with the seconda or coupling coil but substantially out o its inductive influence. Means are provided whereby the effective inductance values of the transformer primary andA secondary, and of the loading coils, or, speaking more generally, the se f induction of the two oscillator circuits, may be varied rapidly and simu taneously in a predetermined manner to change the operating wave length without materially disturbi a previously established desired tune re ationship between said circuits. In the particular form of apparatus shown in the drawings, the transformer primary and seconda 'coils, and the loading coils, together with the necessary operating and controlling means therefor, are here shown supported in compact arrangement as a mechanical unit by means of a substantial insulating framework. This' framework comprises main front and rear plates or panels 30, and 31 respectively, and a sma ler supplemental front plate or panel 32, all rigidly held together in proper paced relation by longitudinally extending tie rods 33, here shown as of metal, incased in heavy insulating sleeves 34 whlch also act as spacingrhr distance members between the panels. e plates or panels are also of suitable insulating4 material. Most desirably, and as here shown, the several coils supported on this framework are flat helical coils of copper ribbon, commonly known as'pancake coils. The oscillation transformer is mounted to one side of the center line of 'the framework and consists of the two parallel coaxial an-r cake coils 35 and 36, the primary co 35 being statiouarily mounted on the rear face of the main front panel 30, while the adjustable secondary or coupling coil 36 is mounted in such a wa as to be movable toward and awa v from die primary by means hereinafter scribed, whereby the transformer couiling distance may be adjusted or varied as esired. In the drawings, the secondary is shown in the position for maximum close coupling. On t e other side of the center lineof. the framework are sup the loading coils 37, 38 39, 40 an 41, these loading coils being electrically connected in sesiesnwith each other, and also arranged for connection in with the transformer secondary and the antenna, in a manner to be hereinafter more fully described. The arrangement is such that the loading coils are within inductive range of each other, but are practically out of inductive range of the transformer. Five loading coils are employed in the present exam ple, since this particular transmitter is designed for quick chan e operation over five different wavedengt s and it is convenient to have the loading inductance diylilled into the samef number drlif sections.

e mechanism or rapi y changing wave lengths takes the form, in this instance, of manual operating means comprising a rotatable operating rod or shaft 42, of insulating material, provided Awith a hand knob 43, said rod serving to connect for movement in unison the primary switch arm 44, secondary switch arm 45, and loading inductance switch arm 46, The pril mary and secondary switch arms are secured, respectively, to insulat' distance collars 47 and 48, collar 48 being best secured to the shaft 42, and collar 47 being loose on said shaft. The several switch arms or blades are respectively arranged for variable connection to the transformer primar and secondary, and the loading coils. hus primary switch arm 44, connected to the shaft 42 by means to be hereinafter described, sweeps over a series of contacts 49, representing different effective inductance vallies of the transformer primary and corresponding in number to the numberof wave lengths at which it is desired the transmitter shall be operable, five in this instance. Stops 50 are provided, one at each end of the series of contacts, which are mounted-on the front anel 32, to suitably limit the movement of t e switch arm. The contacts 49 are connected res tgly hby flexible conductors 51 lea g t ug o nings 51,51",tos cli 52, leach of-ewhich can be adjustglblllygset id any desired position on the rimary coil. Similarly, the secondary switch arm 45 sweeps over a second series of live contacts 53, mounted on the rear frame plate 31, thls second seriesof contacts be' also provided with terminal stops 54. T e contacts 53 are connected to tappin points on the movable transformer secon ary by special means. As here shown, such means comprise conductors 55 connecting' the respective contacts 53 with horizontal conduct' rods 56, which are xed to the rear pane and which extend forwardly and enter hollow insulating supportin isleeves or guides 57, carried by the movab e insulating plate 58. Brushes 59 secured to the sleeves 57 bear upon the conducting rods 56, and are connected by flexible leads 60 to clips 61, five in number, which are adjustable in position on the turns of the transformer lio Secondary coil. The connecting terminals of conductors 55 are best mounted on insul ting spacers", as shown.

'e secondary switch arm 45 may be electrically connectedl in the secondary circuit of the transmitter in series with the loading inductance switch arm 46, in any suitable manner. In this instance, this connection is eected through a flexible lead 62 going to terminal 63 on the conducting bar 64, which latter extends between the` panels 3U and 31, and thus also incidentally constitutes a bracing girder. As is shown most clearly in 10 and 11, the bar or girder 64 provi' es 'at a point intermediate its length a beari for a vertical conducting spindle 65 touhe upper end of which is pinned the switch arm 46. The lower end of the spindle carries-a pin gear segment 66 with which a similar gear se ent 67, carried by the wave change ro 42, meshes. A spring washer 68 placed between the hub of the switch arm 46 and the bar 64, insures good electrical contact between the switch arm and bar. The loading inductance switch arm 46 carries a brush 46IIL which sweeps over a 'series of five contacts 69,70, 71. 72 and T3, mounted in an arc above the frame, as shown. These contacts are respectively connected to adjustable tapping points on the loading coils, in a manner to be hereinafter described.

Loading coils B7 and 41 are supported, as shown, d rectly on the rear anel 31and front panel 30z respectively. e intermediate loading colis 38, 39 and 40 are mounted on intermediate insulating plates 74, and 76, res 'vely. As before stated, the loa-ding colls are connected in series. In order to simpli 'the series connections, and 'at the same time not to interfere with the mutua-l inductive eil'ect of the loadin coils, the following arrangement is particidarly conven'ent. The live coils viewed from one .end of the series, are wound, alternately clockwise and counter-clockwise, and the leads connectin pairs of adjacent coils therefor extend a ternatel between adjacent coil 'pheries and a jacent coil centers. Thus, the connection between coils 37 and 38 is through conducting rod 77 which extends between the outer periphe'ries of these coils. Coils 38 and 39, on the other hand, are connected through rating sprin contacts 78, each of which is secured to t e central or innermost turn of its corresponding coil. In a similar manner, conducting rod 7 oonnects the-outer peripheries of coils 39 and 40; while coperatin spring contacts 80 cdn'nect the centers o colls 40 and 41. At 81 is a binding post whereby the center of coil 37 may be connected directly or indirectly to En antelwl.' An 'other convenient arrangement 'of 'the loading eis ln'ly 'of be'ipoyed.

As before stated, provision is made for connecting each of the several loading coils with its respective contact in the series ol` contacts 69 to T3, over which the loading inductance switch arm 46 sweeps. This provision, is such that the loading coils are successively cut into or out of the secondary circuit by the switch arm 46, us the shaft 42 is turned to change the operating vvavc length. In this way, the propel' amounts oi' primary and coupling inductance, and the proper number of loading coils, for each of the five selected wave lengths, are placed in circuit by simultaneously shiftingthe threc switch devices. It is also desirable that provision be made for varying the proportion of any loading coil actively in circuit easily and rapidly in accordance with operating conditions at the different wave lengths for which thc wave change mochanism may he set. The following arrangement is particularly suitable for the above purposes. A hollow shaft or slccvc 82 of insulating material extends axially through the series of loading coils and through the plates 30, 3T. 74-` T5 and T6. and is rovolubly supported in suitable insulating bushings or hubs 88 which are screwed into the several plates. Stop collar 83 at the rear and sleeve 83h at the front hold sleeve 82 against longitudinal movement. For each loading coil there is a conducting arm or switch device rotatably supported by the corresponding bushing 83. This contact arm comprises a central spider 84 having inwardly extending spaced radial fingers 85, terminating in broad cylindrical surfaced ends 85* concentric with and closely adjacent sleeve 82 which lits loosely therewithin. The spider is radially slotted at 86 to irevent eddy currents. the gap being close by a piece of insulating material 86. Without some such precautiorinoverheating may occur in operation. The spider is rotatably supported on the hub 83 by means of washers or disks 87, which are secured thereto by screws 88 in bosses 88, and which lit easily within u coperating peripheral groove or track on the hub, the broad ends of fingers 85 of the spider projecting into the recess 89 formed in the end of the hub 83 adjacent said spider. A spacing ring 90 of insulating material is secured to the spider 84 by screws 90; and -by means of similar screws (not shown) the metal slip ring 91 is secured to ring 90. said slip ring being electrically connected, as by one or more of said screws, to spider S4. The slip ring is slotted, similarly to the' spider 84, to prevent eddy currents; but the slottin is in a diierent angular position from t e Blotting of the spider, for reasons which will presently appear. A conducting arm 92, integral with spider 84, extends radially to a point about midway begoodelectrical contact with both.

tween the innermost and outermost turn of the loading coil, at which point another conducting arm 93 is hinged to it. The arm 93 carries at its free end a clip or slider 9i which is movable along the conducting ribbon of which the loading coil is formed, so that by rotation of the spider, this clip can be moved to any desired position on the pancake coil. ln order to guard against accidental movement of the clip along the conductor by reason of shocks or jars, a counterpoise 95. may be attached to arm 95 of the spider. Iheemployment of a hinged or jointed contact-'making arm of the char- :icter described has special advantages in connection with large coils like the loading coils here shown, when the conditions of o'peration are such that the potential in the outer turns of such coils is very high due to anto-transformation. This condition is most pronounced when operating at short wave lengths; and for the arrangement of coils here shown is most likely to occur in coils 37, 39 and 41, especially in coil 37. By means of the hinged arm, the difference in potential between the coil conductor and arm 92 never exceeds that due to approximately one-half the total number of coil] turns. It will be noted`thnt the contact arm for coil 37 is spaced farther from the coil than are the arms of the other coils. rlhis is on account of the particularly high potentials in coil 37, and the spacing would have to be still greater were it not for the hinged arm arrangement.

Each spider is connected to its corresponding switch contact 69, 70, 71, 72 or 73, by means of a conducting bar 97, which carries a brush 98 confined between slip ring 91 and the revoluble spider 84, the arrangement being such that the brush always makes ince the slotting of the spider and the slip ring to prevent eddy currents is not at opposite or adjacent points, the brush 98 is always electrically connected to the spider either b direct contact or throu h the slip ring. t will be Anoted that eac of tthe hars 97 is disposed tangentially with respect to the spider with which it makes contact. By this arrangement the force occasioned by friction between the brush 98 and the spider is exerted longitudinally of the bar instead of transversely; and this is an important consideration especially in the specific form of apparatus here chosen for illustration, where the bars 97 are positively held at their up` per ends only. The bars 97 are bent out-AW wardly as shown, extending in a radial direction but well spaced away from the loading coil, then going to a point of connection with the contact corresponding to the particular loading coil in question. Thus, coil il-l is V.connected to contact 73, and 4so on for the other loading coils. Because of the high 1p1-o r diameter, are sawed through potentials normally existing in the end loading coil 37 in operation, 1t is desirableto mount its switch terminal 69 on a relatively lon insulating spacer 99. It has been found un esirable to leave as dead ends those portions of the loading inductance not activel in the secondary or aerial circuit. Accordi-i ingly the last loading coil 41 has its contact stud 73 always connected to the loading switch 46 through lead 99* going to girder 64. This shunts the' unused rtions of the loading inductanc and avoi s unduly high potentials.

Means are provided for selectively retaining any one of the rotatable s iders 84 and its hinged contact arm in or er to adjust the position of the contact cli or slider on the corresponding loading coi A conven` ient and satisfactory mechanism for this purpose is here shown. It' comprises a. selector tube or hollow shaft 100 of insulatin material, within the sleeve 82, and slidably movable longitudinally therein within' limits. This inner tube or shaft 100 contains suitably mounted therewithin live pivoted latches or do 101, one for each loading coil, each late controlled by a spring 102 which tends to force the tail of the latc outwardly through a lonhgitudinal slot 103 provided in the tube, the ve slots 103 in alinement as shown. Normally these latches are held ino rative by their. contact with the inner su ace of the surrounding sleeve 82, but pon rotation of the inner tube 100 relatively to the outerl sleeve througlr different redetermined angles, each of the alined ots in the iinner hibe may be made to register with a slot 104 in the outer tube or casing 82, as will be mhre fully explained later, whereupon the particular latch in question is thrust outwardly by its controlling spring to engage between a pair of the inwardly projecting fingergS on the spider whose arm governs the clip or slider on the correspondilg loading coil. In this position, illustrated or example at the extreme left in 5.,-the latch mechanism for coil `87 is thus gn operatiye position; and with the two tubes 82 and 100 thus coupled together and also coupled to the spider 84, turning of the opent knob 82* will result in shifting the sli in contact around on the helical conductor o? coil 37 into any desired position. A nypraetical method of mounting the latches 101 within the tube 100 ma be ad ted, but that here shown is simpe and e ectlve. Short lengths of heavy walled insulating tubing 105 (if the on tudeally for the greater part of their length to prende chambers 105, Within each of these chambers one of the latches 101 is pivpted en cross pin 101., its contro pnng being anchored to a cross piece .102.

n assembling the selector iis of the five slots of these mounting blocks or tube-sections,

with its latch in place, is inserted into the tube 100, and after being pushed into proper position is secured in place by means of a pin passing through the unsawed end of the lock and into the walls 'of tube 100. In the apparatus of Fi 5 these securing pins are most desirably of insulating material, as indicated at 106, for all the blocks except that st the extreme right, the securing pin 106* for the latter bein of stronger mate rial, such as steel, and a diiering slightly from -the others in form, for reasons which will presently appear.'

In order to provide for easily selecting and operatively positioning the particular latch 101 corresponding to the loading coil whose slider it is desired to adjust, means are lprovided for rapidly and accurately brin ing into registry the 'particular pair of coperating slots 103, 104, through which that latch is adapted to project. In the a paratus here shown, thefront end of t e outer selector tube is provided with five longitudinally extendin slots 108, angular spaced to agree wit the spacing of the slots 104', which may be equiangular', as here, for' convenience. The in 106 is elongated to provide a reduce 107 (Fig. 14), adapted to enter any one 108 selectively. By pulling the inner tube 100 outwardly until the selector pin projection 107 clears the end of selector sleeve 82, where it can move freely in the annular space 107 between the end of the sleeve 82 and the liange 107 of the outer sleeve 83", then rotating the tube rela tively to sleeve 82 .to place the end of the selector in opposite a selected slot 108, and {inally permitting the sleeve 100 to be drawn back by its controlling spring 100, one of the five pairs of coperating slots 1418-104 is thereupon brought into registry, the proper latch member operates, and the telescomg selecto tubes are thus coupled together and to the contact spider of the iticular loading coil whose slider it is deaired to ad'ust. For convenience, an indicater dial 09 is secured as by screws 109 to #lange 107?, Pand carries the numerals 1, 2, 8, 4 and 5, which correspond eral` loading coils. pointer 110 on the operating knob 82 coperaties with the dial. by pulling out the sleeve 100 and then setting the pointer or arrow to. point to the proper number on the indicating dial, the latefineclla1-1ism for couphng the operating knob to the corresponding loading coil autowhen the back into g 100". In this connection it Ould be noted that said controlling is swivel at 100 to the end o# sleeve 82, thus permitting free relative rotational mo between projection/at'The coupling distance may be read of intermeshed pinions complete revolutions turn of the primary sleeve 82, and the inner tube 100. Furthermore, to insure free relative movement' between selector tube 100 and sleeve 82, these members actuall contact only at bearing surfaces 100 an 100". Turning now to the transformer construction, any suitable moans may be provided tor shifting the movable secondary or coupling coil'36 toward and away from the primary coil to var the coupling distance, and in the particu ar construction shown, the movable supporting plate 58 carries fixed thereto a long axial sleeve 112, which terminates in an internally threaded member 113,-preferably of metal, the threads of this member being engaged by external threads 114 of an o erating rod 115 of insulating material, t is rod being rotatable within the sleeve 112 and in a bearing provided at 116 in the rear panel 31. Rotation of the rod can be readily effected by means of knob 117. It will be seen that by rotating the ,knob in one direction the sleeve 112 will be forced toward the rear and will carry with it the movable plate 58 with coil 36 mounted thereon; while turning the knob in the opposite direction will move the secondary coil toward the primary coil. on a scale 112 provided on the sleeve 112. Suit ableI stop means should be provided to prevent forward and rearward movement of the coupling coil or` transformer secondary beyond predetermined extreme itions tor maximum loose coupl' close coupling. This stop means is desirably of such character as to @lard against jamming or forcin of the movable 'As here shown, t is is accomplished by means of a gear stop device mounted at the rear of the apparatus and consisting of 115, and 115", Whdl carry, respectively, stop members 1 15i 4and 115d. Pinion 115, secured to shaft 115, 24 teeth; while pinion 115 which is loose on 22 teeth. The pinions and related that the operbe turned throughten from either limiting position of the Asecondary coil. VThe -stop members ,then Vrome into locking r.y ment and' prevent fu r movement.

Terminal 118 connected t0 the Aouter turn of the secondary coil of .Unister-mer ma be connected ,through pble leed 111,9 an binding p09*' 120 t0 gfQltil V suitable ammeter (not shown). outer transformer .coil naar be connected to the condensate the www circuit through binding post 121 and .lead 122. The variable action to the former primary, represented by the .rimary switch arm 44, is connected to xan al just ye point on the variable induetance Lor venomeir coil 1.23 by yflexible lead 124 and ating shaft 115 may ducting bar 125 (Figs. 6-9), which latter carries a double brush 125l bearing against a contact collar on rotatable conducting shaft 125, to which shaft is-secured switch arm 126 of the variometer. This switch arm is a simple radial arm carryin a contact clip 127 which engages the con ucting ribbon of the variometer coil and which is also longitudinally slidable on the arm 126 as the latter is rotated by means of hand knob 126. he operating handle ma be provided with a guard plate 126". is simple type of contact shifter can be used in this location because the variometer coil is composed of comparatively few turns, and hence there are no dangerous potentials in the outer turns under operating conditions. The outer turn of the variometer coil may be connected to the other side of the closed oscillating circuit, in this instance at the spark gap through lead 128 and binding post 129. This variometer provides a small value of variable inductance which is required in tuning the primary circuit to intermediate wave lengths occurring between the turns of the large rimar coil.

` eturning now to t e mec anical connection of the primary arm 44 of the wave change switch to the wave change shaft or rod 42, this may be elected in any convenient manner. Where the set is tobe always used with a standard aerial of say 450 meters, the arm 44 may be permanently fixed on said shaft. But where the set may ave to operate with aerials, of longer or shorter periods than the standard aerial, it is important to provide means whereby the relation of the primary switch arm of the wave changer to the secondary switch arm 45 and loading linductance switch arm 46 may be `varied. lVarious expedients may be adopted for this purpose. In the arrangement here shown,\the"switch arm 44 is adi'usta'ble on the shaft 42 inte different angu ar positions in the following manner. A sector 130 of insulating materialA isfixedly mounted upon shaft 42. As here shown said sector is` secured by 'means of screws 130* to a collar 130, which in turn is secured by pin 130" to the shaft 42. The sector is rovided at its outer margin with notches 131, which may be conveniently "numbered l1, 2, 3,4 and 5 as shown in Fig. 6. A manuali operable spring catch 132, radially slidab e on the rear face of switch blade 44, is adapted to engage thev notches 131, so' that the witch blade may be shifted to any one of the numbered positions and held in place by the engagement of catch 132 in the correspending notch. When the switch blade is in the No. 3, or normal position, the wave change switch-is arranged to connect in the aerial circuit the proper coupling and loading coil inductan 'for any one of the five very predetermined wave lengths when the aerial employed is of the standard period. Should the aerial be of shorter period, antadditional coil can be added to the aerial circuit by shiftin the primar switch blade from norma osition to o. 2 notch. lVitl) the blade in o. 1 notch, two loading coils are added. This will permit tuning of the set for use with an aerial of approximately 300- meters. When the set is required to operate with aerials of more than 450 meters, the primary switch blade is shifted from the normal to No. 4 notch, which decreases the inductance in circuit with the aerial coil. A shift from normal to No. 5 notch cliects a decrease by two loading coils.

eferring again to the mounting of the loading coils, the arran ement described has important practical advantages as above pointed out. But this entails having two supporting plates 74 and 75, between coils 38 and 39; and, similarly, two plates 76 and 30, betweencoil's 40 and 41; the coils of each pair being thus mounted back to back. -Each coil is mounted on its su porting plate by means of studs 133, whic extend through the supporting plate and through spacers 134, desirably of insulating material, notched as shown to receive the rib n conductor, each'stud being hooked at 135 to engage the conductor, and being threaded at the other en for engagement by a securing nut 136, which is received in a counter-sink on the back of the supporting plate. The backs of the plates in the two pairs, 474-'75 and 0,-lue necessarily rather close together in this,design of apparatus, and hence special precautions are taken to prevent current jumping across from the mounting studs of one coil to the studs or even tothe turns of the adjacent coil. This is likely to occur only, in theouter portions of coils whose peri heries are not directly connected, where t e potential'dilferencesare often high. Jumping across between the mounting studs is 'guarded against by staggeringf the ,studs in some way. As here shown, the studs of each coil are arranged in six radial sets or series, and the sets are staggered in the successive plates, so that the stud sets of adjacent coils do not come opposite. But there is nevertheless the tendency in the' outer 'coil turns for current to jump from the studs of one coil to the turns cf the next adjacent coil; and since vthe dielectric` constant of any solid insulating material is higher than that of air, this tendency would be furthened by the presence oirthe supporting plate interposed between such studs and coil turns. Accordingly, apertures 137, circular in the present example, arefo.v ixlici 74 7s e'iics'ilgach of the su porting'p ates y5, `6 an A l opposi thi) outer coil turns and between' the radial sets of studs. It is apparent therefore that in each pair of coils in question, the studs supporting the outer turns are separated from the outer turns of the next ad'acent coilby an unobstructedair space. t the same time almost none'of the strength and rigidity inherent in the use of solid supporting plates, so essential especially for apparatus intended for military purposes, is sacrificed.

A novel detail of considerable practical importance is the construction of the contact clips shown at 52 and 61 for adjustable connection of the primary mnd secondary contact studs to the transformer coils 35 and 36. As shown in Figs. 4, 21, 22 and 23, each contact clip is a laminated structure comprising three resilient metal strips 140, 141, and.142, which are secured together` by rivets 143. The strip 140 is lon 'tudinally slotted to form four fingers, o which the two outside fingers 144 extend beyond the two intermediate fingers 145, and are bent at theirprojecting ends, as shown. 141 is slotted in such a way as to provide five fingers, of which the central finger 146 extends beyond the others and is bent similarly to fingers The two pairs of fingers 147 on either side of finger 146 are of substantially the same length as fingers 145, and like them are tapered or beveled at their free ends. The strip 142, lying between strips 140 and 141- is considerablyshorter .than the two outer strips and is not slotted. Viewing the contact cli from one edge., it will be seen that the dou le bends in the fingers 144 and 146 are such that said fingers appear to converge or inte sect ,and then diverge again. distan between the line of convergence and the free end of intermediate plate 142 is substantially equal to the width of the copper ribbon, of which the ancake coils 35 and 36 are wound. The e of a lead 148 may be connected to .the clip byA means of a bifurcated socket 149 which slips over the opposite end of the clip between the rivets. at which point the clip may be notched as .shown at 150. After inserting the end of the had in the socket, both the socket and the lead may be firmly soldered to the clip to iorm an integral construction.

The manner of employing this type of dip is su'ciently obvious. B y presenting the ends of the fingers 144 and 146 to the edge of the ribben conductor, so that the divergent ends straddle the conductor edge, and then pushing the clip lfirmly into place, the fingers 144 and 146 first are moved apart to guide the conductor edge yaccurately between the coperating sets of contact fingers 145 and 147. and then s' ing toward each other again to engage th); farther odge of *the ribbon conductor. In the the The strip 144 but oppositely thereto.-

first mentioned edge of the conductor has come into abutment with the end of the intermediate strip 142. It is evident that this arrangement provides a clip which can be accurately and rapidly applied to the conductor, and which embraces the same firmly enough `to adequately guard against accidental displacement.

The electrical relation between the various parts of the apparatus has been indicated in the foregoing detailed description, and said relation is also clearly indicated diagrammatically in Fig. 24 where the parts previously referred to in this description bear the same reference characters, so far as necessary. 4For the sake of Iclearness the mechanical connection between the switch arms 44, 45 and 46 is not shown in this diagram. A short-circuiti? connection 151 between primary stud o. 5 of the wave change mechanism and the pivotedend of switch blade 44, shunts all unused turns of the primary transformer coil. This provision is made to eliminate high potentials and consequent brushing of the primary circuit. Ini connection with the wave change mechanism as previously described, the diagrammatic showing of Fig. 24 indicates thaty operating the wave change shaft to increase or decrease the wave length, always increases or decreases all three of the variable inductance factors, namely, the primary inductance, couplin inductance, and loading inductance. Thls is not necessarily so, how.- ever, in the case of the cou ling inductance. In tuninflr the circuits for tlie different wave lengths, 1t frequently happens that the adjustable taps on the secondary or coupling coil, have to be set in such manner that the coupling inductan both increases and decreases during a complete movement of the wave changer in either direction over the entire range of wave lengths. 0f cou-rse the primary and secondary indnctances, considered as entireties, alwa s increase or decrease for increase or Areaae in wave length. I have also found that by a suitable adjustment of the various parts and connections, the several tappingpoints onk the secondary or coupling coil can be concentrated within a comparatively short length of the conductor composing said coil, in some instanresl on a single turnof said conductor. It is possible eren to use but a single tapping point on the coupling coil, thus eliminating the secondary switch arm 45; but with such an arrangement the 4operator is required to adjust the coupling at the different wave lengths more than is necessary when several tapping points are nsed in the coupling coil.

The manner of operating the transmitter apparatus herein described is sufficiently obvious to those skilled in the art from the foregoing description, but will nevertheless be briefly summarized. Assumi the set to be employed with a standard aerial, the operator first adjusts the apparatus for operation at five definite wave lengths which in practice may be 600, 825, 1200, 1500 and 2,000 meters. The proper positions ofI e adjustable contact clips 52 on the prima coil 35, corresponding to the selected wave lengths, may be closely approximated b reference to the scale appearing lat the leigtY of the sector opening in panel 30, as shown in Fig. 1. In order to efect the complete adjustment, it is necessary to tune the oooperating oscillation circuits for each of the live operating wave lengths. For instance, with the switch blade 44 set at normal in notch No.' 3 of sector 130, the wave changer is moved if necessary to place switch blade 44 on primary contact stud 1. In'this position of the wave changer, switch blades 45,

and 46 will also contact with the No. 1 studs of their respective series. The general method of tuning the circuits for any given wave length is well understood by those skilled in the art and requires no detailed explanation here except as regards manipulation of the specific apparatus shown. 'In

.order to makethe necessary adjustment of inductance in the aerial circuit for tuning at the rst wave length, 600 meters, the o erator pulls out the selector rod, turns e handle until the arrow 110 oints to the numeral 1, indicatin the first oading coil, and then releases the andle, said handle bein thereu n coupled to the movable switl arm o loading coil No. 1 by operation of t e selective latch mechanism hereinbefore described. The selector handle may then be rotated to increase or decrease the aerial inductance to the necessary extent. ,The coupling of the circuits maybe adjusted by rotating the coupling handle 117 in either direction. The foregoing operations are repeated for. all ve wave lengths, the wave change device being of course loperated to bring the switch blades-44, 45 and 46 into contact with the remaining studs oftheir respective series successively, and the aerial inductance beinladjusted in each case by selecting and s 'fting the rotary contact arm on the articular loading coil corresponding to t e wavp length for which adjustment is being made. When the transmitter has been tuned, and coupled in the above manner at all five wave le hs, the operator may shift lfrom one wave to any other of the selected wave 1 b moving the wave change switch to -mary stud corresponding to the wave length desired. This is not only an advn in the general operation of the set, but may he used in secret-transmission by coding the. wave lengths according te a prearranged schedule;

Wha-eitisneceesarytadjustthetnna- 4of illustration. The clips mitter for operation with serials of either longer or shorter periods than the standard aerial above assumed, the procedure for tuning and coupling is in general the same. However, if the aerial is of longer period than the standard, and assuming it 1s desired to tune the circuit for a wave length of 1200 meters, that is, with the wave change switch blade 44 on rima stud No. 3 the operatorshifts saidpswitg blade to tact with No. 3 stud. This decreases the aerial inductance byone loadin coil, and the selector rod must be move to adjust No. 2 loading coil. If resonance is not obtained within the r of this coil, the switch blade is shifted to No. 5 notch while remainin on No. 3 stud. This decreases the aeria` inductance by two loading coils, and the selector rod is then moved to adjust No. 1 coil. Similarly, if the aerial is of shorter period than, standard, switch blade 44 is ect in No. 2 notch, and then in No. 1 notch if necessary, resulting in the addition of one and two loading coils, respectively, and the selector rod being moved to connect with No. 4 or No. 5 l coil, as the case may be, to effect final adjustment of .the aerial inductance.

From the fore ing, it will be seen that the additional a justments necessitated b operation with serials which are not stan ard, amount mechanically to -changing the normal relation between the simultaneousl movable primary and secondary switch blades or. armatl'lThis necegsarily 'edues to some extentm e range' .o wave engt s over lwhich the wave change mechanism can be operated, as compared toits o Y ation with .a\standard antenna; but o erwise the general principle of simultaneous variation of electrical values in the ating circuits simultaneously is not altered.

It is obvious that the set can beadjusted vfor operations of wave l hs intermediate those arbitrarily selected a ve :pr purposes on e transformer coil can be shifted il) necessary to give the exact number of primary turns for each desired wave and the can than be tuned such selected wave rlength in already described. Thm ha y the wave then` conin the encarta the proper primary turns, coupling inductance, and aerial in- Y ry -dactancenecessary for the indicated pri- MUFW@ lmgth- By careful adjustment of the transmitter Y or' the different wave lengths selected,

'only Velsligh' t adjustment of the conpli if a from :Ed

necessary in shifting length u another. i

features shown and disclosed, but not claimed, in the present application are o. 4 notch, but leaves the blade in con-- disclosed and claimed in a copending divisional application, Serial No. 341,990, filed December 2, 1919.

Whatl claim is:

1. Radio transmitter apparatus comprising in combination, substantially parallel main front and rear plates or panels arranged a suitable distance apart and connected together to form a unitary supporting structure, a pancake inductance coil stationarily mounted on the front panel and constituting a transformer primar a plate intermediate said main plates an parallel therewith and mounted for. movement forwardly and rearwardlyz a second pancake inductance coil cons tutmg the transformer secondsiry mounted on said intermediate late in inductive relation to the primary coil and substantially coaxial therewith, means for movin said intermediate plate to vary the trans ormer couplin distance, a plurality of substantiall parel el pancake coils electrically connecte in series and constituting loading inductance, said coilsV being mounted upon said supporting structure in parallel spaced arrangement on an axis substantially parallel to that of the transformer coils, a set of contacts electrically connected to adjustable taps on said primary transformer coil, a second set of contacts electrically connected to adjustable taps on said secondary transformer coil, a third set of contacts each electrically connected to an adjustable tap on one of said loading coils, a separate movable switch member for each set of contacts, the secondary coil switch member and the loading coil switch member being electricall connected in series, and `means mechanical y connecting the three switch members and operable to move them simultaneously whereby the inductance values of the primary, seconder and loading coils in circuit may be vari in a predetermined manner.

2. Radio transmitter apparatus comprising, in combination, a rigid supporting structure, a ilat coil stationarily `mounted thereon and eonstitutix the rimary o f a transformer, a second at coi constitutin the transformer seconda mounted on sai structure substantially coaxially with the rima coil and movable toward and away m e a plurality of liatloading coils electrica y connected in series supported by d structure on a common axis substantially A, rallel to the transformer axis but to one side thereof, a set of contacts electrically connected to ad'ustable on said primary coil, a secon of contacts electrically connected to adjustable ta on sa'd second coil, both sets of coiistacts bei arr in planes substantiall to the trans ormer coils, a third Vset of coinzactsarranged in a plane transverse to said transformer and loading coils, each of said third set being electrically connected to a variable point on one of said loading coils, a switch coperati with each said set of contacts the switc es for the second and third sets being connected in series, and means connectin all said switches mechanically and opera le to move them in unison.

3. Radio transmitter apparatus comprising, in combination, an oscillation transformer, a plurality of loading coils in circuit with the transformer secondary, three sets of contacts of which two sets are connected, respectively, to adjustable tapping points onI the transformer primary and secondary and are in paral el arrangement, while the third set is connected to adjustable tapping points on the loading coils, and has its constituent contacts lying in a plane transverse to the first two sets, separate switches co rating respectively, with the three sets o contacts, and means mechanically connecting said switches and operable to move them all in unison.

4. Radio transmitter apparatus comprising, in combination with a supporting structure, a transformer having flat primary and secondary coils coaxially mounted on said structure, the secondary coil being movable with respect to the primary coil to vary the coupling distance a set of contacts mounted near one end of said structure, adjacelt the transformer primary and connected to ta ping points on said primary, a second set o contacts mounted near the op end of said structure and connecte to tapping points onvthe transformer secondary, switches respectively coperating with said sets of contacts, an o erating shaft mechanically connecting sai switches and rotatable to move them both, a plurality of flat loading coils in circuit with the transformer secondary and mounted op said structure at one side of the transformer, a third: set of contacts, each contact mounted adjacent a loading coil and electrically connected thereto, said third set of contacts extending intermediate the ends of said structure, a switch coperating therewith, and means connecting said switch with said operating shaft.

5. Radio transmitter apparatus comprising, in combination, a variable transformer consisting of relatively movable rimary and seconda coils, loading in uctanee coils 'in circuit with the transformer secondary and located in substantially noninductive relation to said transformer, u substantially unitary structure su porting the foregoing parts, control means or varying the coupling distance between the transformer primary and secondary, switches movable to vary the inductance of the transformer primary and secondary, respectively, a third switch movable to vary the number 

